The derivatization of known insecticide compounds to produce novel compounds which exhibit improved properties such as greater residual effectiveness, lower mammalian toxicities and still retain their insecticidal activity continues to provide new and useful insecticides. Efforts with carbamate insecticides in particular have yielded a variety of new insecticidal compounds such as those described in DE 3,205,195, European Patent application EP-113-317-A, and those described in J. Agr. Food Chem. Vol. 21, No. 5 (1973) and Vol. 26, No 3 (1978) by T. R. Fukuto, et al. The continuing effort and promising results obtained in this area of research has renewed interest in the potential for a new generation of improved carbamate insecticides.
The present invention is novel insecticidal carbamate derivatives of formula I ##STR1## wherein R is H, C.sub.1 -C.sub.4 lower alkyl, benzyl and salts of the acid. The novel carbamates of formula I in which the COOR group is in the o, m, and p, position and represents a carboxylic acid function, a carboxylate salt function, and a carboxylic ester function have been found to be highly effective insecticides, which possess systemic insecticidal activity and exhibit greatly reduced mammalian toxicity compared to carbofuran, the carbamate insecticide from which they are derived.
Preferred formula I compounds are those in which R is H, C.sub.1 -C.sub.4 alkyl, and salts of the acid wherein R is a salt-forming cation such as a cation of alkali metals, such as sodium, potassium; alkaline earth metals; manganese, copper, iron, zinc, cobalt, lead, silver, nickel, ammonium or organic ammonium wherein preferred organic ammonium salts are defined as a group consisting of a positively charged nitrogen atom joined to from one to four aliphatic groups each containing one to 20 carbon atoms. Among the organic ammonium groups which are illustrative for the preparation of the aliphatic ammonium salts of the formula (I) benzoic acids herein are: monoalkylammonium, dialkylammonium, trialkylammonium, tetraalkylammonium, monoalkenylammonium, dialkenylammonium, trialkenylammonium, monoalkynylammonium, dialkynylammonium, trialkynylammonium, monoalkanolammonium, dialkanolammonium, trialkanolammonium, C.sub.5 -C.sub.6 -cycloalkylammonium, piperidinium, morpholinium, pyrrolidinium, benzylammonium and equivalents thereof.
The compounds of the invention may readily be prepared by the reaction of carbofuran with oxalyl chloride in a temperature range of 0.degree. C. to 150.degree. C. and preferably 60.degree. C. to 120.degree. C. in an inert organic solvent such as ethers (diethyl ether, dioxane or tetrahydrofuran), hydrocarbons (such as benzene, toluene or xylene), chlorinated hydrocarbons (such as chloroform, dichloroethane or chlorobenzenes), and nitriles, ketones and esters, and mixtures of these solvents.
The hydrogen chloride formed in the reaction can be flushed out with gases, such as air or nitrogen, or escapes owing to the reaction temperature. Sodium carbonate, sodium bicarbonate or a tertiary organic base, such as triethylamine, benzyldimethylamine or N-N-dimethylaniline, may be added to the mixture to neutralize the acid.
The thus-formed product may then be reacted with an o, m or p-hydroxybenzoic acid ester in an inert organic solvent as described above in the presence of a base as described above to yield the desired formula I compound as illustrated in Flow Diagram (I) below.
Formula I compounds wherein R is H may then be prepared from the esters by hydrogenation of the thus-formed esters.
If a salt of the benzoic acid is desired, the thus-formed formula I compound wherein R is H may be reacted with the appropriate base in suitable solvent such as water, an alcohol, ether, hydrocarbon or chlorinated hydrocarbon solvent. If the isolation of the salt is desired, the reaction is preferably conducted in an organic solvent which may be removed by distillation under reduced pressure. ##STR2## wherein R is C.sub.1 -C.sub.4 alkyl, or benzyl.
The novel formula I compounds of the invention are exceedingly effective for the control of a wide variety of insect pests.
For the control of insects, including soil insects, which attack growing plants and/or harvested crops, including stored grain, the insecticidal compounds of this invention may be applied to the foliage of plants, or onto the soil in which the plants are grown, the insects' habitat and/or the insects' food supply. The active compound may be applied in the form of a dilute liquid spray; however, it may also be formulated as an emulsifiable concentrate, flowable concentrate, aerosol, dust, wettable powder, granules or the like.
These formulations may be produced by known procedures, by mixing the active formula (I) compound with inert liquid or solid diluents and carriers, optionally containing surface-active agents such as surfactants, wetting agents, dispersing agents and the like.
Some examples of liquid diluents, carriers, and solvents, that are suitable include, aromatic hydrocarbons, such as xylene, toluene or alkyl naphthalenes, chlorinated aromatic or chlorinated aliphatic hydrocarbons, such as chlorobenzenes, chlorethylenes or methylene chloride, aliphatic or alicyclic hydrocarbons, such as cyclohexane or paraffins, mineral oil fractions, alcohols, such as butanol or glycol as well as their ethers and esters, ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, or strongly polar solvents, such as dimethylformamide and dimethylsulphoxide, and water.
Solid carriers that may be used include ground natural minerals, such as kaolins, clays, talc, chalk, quartz, attapulgite, montmorillonite or diatomaceous earth, and ground synthetic minerals, such as highly-dispersed silicic acid, alumina and silicates, crushed and fractionated natural rocks such as calcite, marble, pumice, sepiolite and dolomite, as well as synthetic granules of inorganic and organic meals, and granules of organic material such as sawdust, coconut shells, maize cobs, tobacco stalks and the like.
Suitable surface active agents include nonionic and anionic surfactants, such as polyoxyethylene-fatty acid esters, polyoxyethylene-fatty alcohol ethers, for example alkylaryl polyglycol ethers, alkyl sulfonates, alkyl sulfates, aryl sulfonates lignin sulfonates and the like.
Formulations in general contain from 0.1% to 95% by weight and preferably 2% to 50% by weight of the active formula I compound.
The invention is further illustrated by the examples below, which are presented as illustrative and are not to be considered as limitative.